Evaluation of the intra-arterial wall surface is necessary for control of laser ablation of tissue. Angioscopy produces clear observation of the target sites, provided adequate irrigation of the vessel with saline solution is maintained. Precise quantitative location of the target is difficult. In addition, size constraints may limit angioscopy's usefulness in the coronary vessels. Preliminary fluorescent observation of atheromas and normal aortic specimens from humans was performed using a fluorescence microscope with 450-490 nm excitation. Fluorescence spectra collected using a multi-channel analyzer indicated clear intensity differences between the normal and atheromatous tissue. These differences were eliminated by ablation of the atheroma by either an argon laser (514nm) or a xenon chloride (308) excimer laser. Further fluorescent detection schemes using fiber optic probes in patients have utilized laser excitation at 325nm and 337nm, and detection from 375nm to 625nm. Realtime spectral analysis and algorithm detection of normal/abnormal arterial surfaces has been proved feasible for guiding plaque and thrombus ablation. Clinical trials of fluorescence-guided later angioplasty are currently underway in both peripheral and coronary arteries.